BigCommerce blog functionality is very simple and pared down OOTB. Backend fields are as follows:

• Title (text)
• Body (WYSIWYG)
• Author (text)
• Tags (text)*
• Summary thumbnail image*

*optional field

Should more customization be needed, BigCommerce recommends using the Shogun page builder app, which offers maximum customization of page layout and elements. Subscription to the app is $49/month.